As maternal employment during the first three years of children's lives has increased, whether and how the use of nonmaternal care (i.e., by fathers, relatives, nannies, family day care homes, and daycare centers) affects the mother-child relationship and child development has been of great interest to researchers and policy makers. Much research has examined the effects of nonmaternal care on child outcomes, but inadequate attention has been paid to the possibility that mothers' parenting may also be affected by nonmaternal care. Given that mothers' parenting is greatly affected by the contexts of their lives and is a strong predictor of child outcomes, it is important to investigate this possibility. Studies that examined the link between nonmaternal care and mothers' parenting largely relied on attachment theory. This theory contends that time spent apart from her child hinders a mother's ability to learn about her child's cues, which in turn reduces her ability to provide sensitive responses to those cues. Despite its popularity, this approach is limited in part because there is little empirical evidence that the use of nonmaternal care is related to mothers' lower ability to learn their children's cues. It also fails to explain how different aspects of nonmaternal care, other than the amount of time, may influence mothers' parenting. Further, it ignores subgroup differences depending on parental resources. Empirical findings have been inconclusive, in part because of inconsistencies in sample characteristics and aspects of nonmaternal care examined. The proposed study extends the prior research on the relationship between nonmaternal care and mothers' parenting behaviors in three ways. First, it uses an alternative perspective, which focuses on mothers' stress and well-being as a mediator for the link. Drawing on the ecological perspective of parenting and the stress process model, the proposed study predicts that some nonmaternal care characteristics, such as type, quality, amount, reliability, and stability of care, have the potential to expose mothers to greater daily hassles and chronic stress, which in turn may lead to poorer mental health and poorer parenting. Second, it assesses whether resources at work and home (e.g., job quality, perceived general social support, marital status, and marital quality) moderate the links between nonmaternal care and mothers' parenting. Third, it uses data from the NICHD Early Child Care and Youth Development, a panel of children and their mothers from diverse geographic regions, economic backgrounds, and ethnic groups with detailed information about nonmaternal care characteristics, which allows me to examine variations by parental resources. This study will contribute to research in multiple disciplines, including developmental psychology, family studies, sociology, and public health by shedding light on the role of nonmaternal care in shaping mothers' parenting. The results of this study can have policy implications, addressing the importance of the availability of reliable and high-quality child care for the well-being of mothers and their young children.